This invention relates an improved biological reaction platform which can be used for a wide variety of assays, for example, automatic immunostaining of tissue sections, in situ DNA analysis, immunoassays such as ELISA, and the like. The automatic device of this invention can be used to process a large number of samples such as tissue sections mounted on slide surfaces using agents and protocols preselected by the operator, while maintaining the slide surfaces in a substantially horizontal plane throughout the incubation cycles.
Immunostaining and in situ DNA analysis are useful tools in histological diagnosis and the study of tissue morphology. Immunostaining relies on the specific binding affinity of antibodies with epitopes in tissue samples, and the increasing availability of antibodies which bind specifically with unique epitopes present only in certain types of diseased cellular tissue. Immunostaining requires a series of treatment steps conducted on a tissue section mounted on a glass slide to highlight by selective staining certain morphological indicators of disease states. Typical steps include pretreatment of the tissue section to reduce non-specific binding, antibody treatment and incubation, enzyme labeled secondary antibody treatment and incubation, substrate reaction with the enzyme to produce a fluorophore or chromophore highlighting areas of the tissue section having epitopes binding with the antibody, counterstaining, and the like. Each of these steps is separated by multiple rinse steps to remove unreacted residual reagent from the prior step. Incubations are conducted at elevated temperatures, usually around 40xc2x0 C., and the tissue must be continuously protected from dehydration. In situ DNA analysis relies upon the specific binding affinity of probes with unique nucleotide sequences in cell or tissue samples and similarly involves a series of process steps, with a variety of reagents and process temperature requirements.
Automated systems have been explored to introduce cost savings, uniformity of slide preparation, and reduction of procedural human errors. Stross, W. et al, J.Clin.Pathol. 42:106-112 (1989) describes a system comprising a series of baths positioned under the circumference of a circular, rotatable disc from which slide trays are suspended. The disc is lifted to lift slide trays from their baths, turned to position the slide trays above the next consecutive bath, and lowered to immerse the slide trays in the baths. This operation can be automated with suitable timers and switches. This system exposes each of the slides to the same treatment and relies on dipping for application of reactants and rinsing.
Stark, E. et al, J.Immunol.Methods. 107:89-92 (1988) describes a microprocessor controlled system including a revolving table or carousel supporting radially positioned slides. A stepper motor rotates the table, placing each slide under one of the stationary syringes positioned above the slides. A predetermined volume of liquid, determined by a dial, is delivered to a slide from each syringe. Microprocessor controls are provided.
Cosgrove, R. et al, ACL. pp 23-27 (December, 1989) describe an immunostaining apparatus for auto-pipetting reagents into a slide well from a carousel holding up to 18 reagent vials. Below each well, a coverplate spaced from the surface of each slide provides cover and defines a reagent flow channel. The slides are suspended at a steep angle. Reagent from the well flows downward over the slide surface. A row of slides are suspended for sequential treatment. Washing is accomplished by a 3 to 4 minute continuous running wash over the sample, yielding an estimated 20:1 wash/reagent ratio.
Brigati, D. et al, J.Histotechnology 11:165-183 (1988) and Unger, E., Brigati, D. et al, et al, J.Histotechnology. 11:253-258 (1988) describe the Fisher automated work station using capillary gap technology. A coverplate is placed over the slide, forming a capillary gap. Liquid is introduced into the capillary gap by placing the lower edge of the plate-slide pair in a liquid. Liquid is removed by placing the lower edge of the plate-slide pair on a blotter. The system is further described in U.S. Pat. Nos. 4,777,020, 4,798,706 and 4,801,431. The previously known devices are limited in their performance and unable to satisfy the needs for automated, high precision immunohistology.
It is an object of this invention to provide a device which provides more rapid, reliable and more reproducible results than standard methods; can perform any standard immunochemical assay including assays relying on immunofluorescence, indirect immunoassay procedures, peroxidase anti-peroxidase methods, or avidin-biotin technology; preforms all steps of the immunohistochemical assay irrespective of complexity or their order, at the time and temperature, and in the environment needed; and is cost effective in terms of equipment, reagent and labor costs.
The automated biological processing apparatus of this invention comprises a reagent carousel cooperating with a sample support carousel to apply a sequence of preselected reagents to each of the samples with interposed mixing, incubating, and rinsing steps cooperating therewith. The slide support carousel has a plurality of slide supports thereon and drive means engaging the slide support carousel for consecutively positioning each of a plurality of slide supports in a reagent receiving zone. The reagent carousel has a plurality of reagent container supports thereon and drive means engaging the reagent carousel for rotating this carousel and positioning a preselected reagent container support and associated reagent container in a reagent supply zone. The apparatus has a reagent delivery actuator means positioned for engaging a reagent container positioned on a container support in the reagent supply zone and initiating reagent delivery from the reagent container to a slide supported on a slide support in the reagent receiving zone.
The apparatus preferably has bar code readers positioned to read bar codes on the sample containers or slides and on the reagent containers. Each of the carousels have homing systems containing a detectable component and a proximity detector therefor for indexing the position of the reagent containers and slides.
One particular advantageous feature of the present invention is that by employing a computer control arrangement to control the positioning of the reagent and slide support carousel, different reagent treatments can be individually performed for each of the various tissue samples by appropriate programming of the apparatus. Additionally, the provision of the bar code readers permits tracking of each of the tissue samples as well as a record of the reagents applied thereto.
The apparatus preferably has a heating chamber means surrounding the slide support carousel for heating slides supported thereon to a predetermined temperature. The heating chamber means includes a hot gas manifold having a plurality of hot gas outlets positioned above the slide supports. The heating chamber means includes a temperature sensor and a hot gas control means connected to the temperature sensor for increasing heat supplied to gas flowing through the manifold and for increasing the hot gas flow rate if further heat is required to maintain the heating chamber at a preselected temperature. The temperature sensor is a thermistor, the tip thereof being enclosed in a heat sensitivity reducing jacket. The hot gas control system includes two heating components with separate controls and a speed control for the hot gas fan.
The drive means engaging the slide support carousel is also a means for consecutively positioning each of a plurality of slide supports at rinse zone, an evaporation control liquid and reagent receiving zone, a vortex mixing zone including vortex mixing means, and an incubation zone formed by the heating chamber means.
According to a first embodiment of the rinse zone, rinse spray means are positioned adjacent to the rinse zone for applying pulses of rinse liquid to the surface of each of the slides positioned in the rinse zone. The apparatus slide supports are, according to this first embodiment of the rinse zone, pivotally mounted for pivotal motion from a horizontal slide incubation position to a tilted slide draining position following each pulse of rinse liquid.
According to a second embodiment of the rinse zone, first and second rinse spray means are respectively positioned only at the beginning and end of the rinse zone, so as to be spaced from one another. The first rinse spray means deposits a layer of rinse liquid onto a slide upon entering the rinse zone and the second spray means, after a predetermined waiting period, uses pulsed streams of rinse liquid, alternately directed at the longitudinal edges of the slides, to knock the previously deposited layer of rinse liquid off of the slide as the slide exits the rinse zone. According to this second embodiment of the rinse zone, the apparatus slide supports are stationary, a jet drain being provided at, for example, the end of the rinse zone, which directs a stream of fluid, such as, for example, air or the like, over the slide to drain any remaining rinse liquid off of the slide surface.
The apparatus preferably has a volumetric pump means, and a reagent delivery actuator means positioned for activating the volumetric pump means, thereby effecting delivery of reagent from a reagent container by the volumetric pump to the reagent delivery zone. An evaporation inhibitor liquid application means is positioned adjacent the reagent delivery zone.
Vortex agitation means are positioned adjacent the agitation zone for stirring reactants on a slide supported in the vortex agitation zone.
The pivoting slide support has distal and proximal ends, the distal end having raised terminal and lateral distal guide tabs with guide termini. The proximal end has first and second lateral guide tabs with opposed slide engaging surfaces for engaging and holding the lateral edges of a slide. The guide termini are lower than the upper slide surface plane. In this embodiment of the slide support, the slide support surface is tipped or pivoted by a tipper to drain rinse liquid from the surface of the slide.
The stationary slide support has a slide support platform at a proximal end and a slide support post at a distal end thereof. The distal end also has raised lateral distal guide tabs with guide termini between which a slide is positioned. The slide support platform at the proximal end has a guide edge and a slide clamping arrangement for clamping a slide to the support platform without interfering with the reading operation of the bar code reader. The distal guide termini are lower than the upper slide surface plane to prevent wick-off of liquid on the slide surface. In this embodiment, rinse liquid is drained from the surface of the slide employing a jet drain which directs a stream of fluid, i.e., gas or liquid, over the slide surface.
An improved biochemical method of this invention with increased sample dehydration protection comprises carrying out a biochemical reaction under a layer of evaporation inhibiting liquid. The improvement comprises (a) covering the sample with an aqueous surface layer by applying an aqueous solution to a planar support surface adjacent a biological sample mounted thereon; and (b) covering the aqueous surface layer with an evaporation inhibiting liquid layer by applying the evaporation inhibiting liquid to the planar support surface adjacent the biological sample in an amount sufficient to form a continuous layer of evaporation inhibiting liquid over the sample. The evaporation inhibiting liquid is substantially water-insoluble, substantially water-immiscible and substantially non-viscous; has a specific gravity less than water, and a boiling point above 50xc2x0 C.; and is devoid of chemical characteristics which would significantly interfere with biochemical reactions carried out on the sample. The biological sample can then be optionally treated (c) with an aqueous reagent solution by applying the reagent solution to the planar support surface adjacent the biological sample. The reagent solution flows to the biological sample under the evaporation inhibiting liquid layer, and the sample is continuously protected from dehydration by the evaporation inhibiting layer.
In another aspect of this invention, the reagent solution is stirred on the surface of the biological sample by applying at least one gas stream to an area of the surface of the evaporation inhibiting liquid layer between the center of the evaporation inhibiting layer and the edge of the planar support surface, the gas stream having a central axis forming an acute angle with the planar support surface. According to one embodiment of the present invention, the reagent solution is preferable stirred by a vortex formed by applying two off-center gas streams, flowing in opposite directions, to the surface of the evaporation inhibiting liquid layer. According to a further embodiment of the present invention, the reagent solution is stirred by a vortex formed by applying a single gas stream along a longitudinal edge of the slide, the gas stream originating from the distal edge of the slide.